System for retrieving a tubular element from a well

ABSTRACT

A system is disclosed for retrieving a tubular element extending into a subsea well provided with a wellhead, the tubular element being provided with a hanger suspending the tubular element at the wellhead, the hanger having a larger outer diameter than the tubular element. The system comprises a conduit assembly having a passage providing fluid communication between the wellhead and an offshore platform located above the well, the conduit assembly having at least an upper part of internal diameter allowing the tubular element to pass therethrough. The system further includes disconnection means for disconnecting the hanger from the tubular element, and retrieval means for retrieving the tubular element through the conduit assembly to the offshore platform.

[0001] The present invention relates to a system and a method forretrieving a tubular element extending into a subsea well provided witha wellhead, the tubular element being provided with a hanger suspendingthe tubular element at the wellhead, the hanger having a larger outerdiameter than the tubular element. The tubular element can be, forexample, a production tubing for the production of hydrocarbon fluidfrom a subterranean formation. Such production tubing is near its lowerend generally sealed to the wellbore casing by a production packer, andis at its upper end connected to a production tree from which theproduced fluids are transported to a storage device.

[0002] A problem arises if the tubular element has to be retrieved fromthe well to an offshore platform (such as a floating platform), forexample because the tubular element has suffered damaged. Since a columnof wellbore fluid extending from the platform into the well is neededduring retrieval of the tubular element an offshore conduit, alsoreferred to as offshore riser, is to be installed between the platformand the wellhead. Retrieval of the tubular element together with thehanger through the conduit requires the conduit to be of relativelylarge diameter. Consequently the conduit is heavy, and the platform hasto be suited to the heavy conduit.

[0003] It is an object of the invention to provide an improved systemand method which overcomes the aforementioned problem, whereby the needfor a relatively heavy offshore conduit and consequent large platform isobviated.

[0004] In accordance with the invention there is provided a system forretrieving a tubular element extending into a subsea well provided witha wellhead, the tubular element being provided with a hanger suspendingthe tubular element at the wellhead, the hanger having a larger outerdiameter than the tubular element, the system comprising:

[0005] a conduit assembly having a passage providing fluid communicationbetween the wellhead and an offshore platform located above the well,the conduit assembly comprising at least an upper part of internaldiameter allowing the tubular element to pass therethrough;

[0006] disconnection means for disconnecting the hanger from the tubularelement; and

[0007] retrieval means for retrieving the tubular element through theconduit assembly to the offshore platform.

[0008] In another aspect of the invention there is provided a method ofretrieving a tubular element extending into a subsea well provided witha wellhead, the tubular element being provided with a hanger suspendingthe tubular element at the wellhead, the hanger having a larger outerdiameter than the tubular element, the method comprising:

[0009] installing a conduit assembly having a passage so that thepassage provides fluid communication between the wellhead and anoffshore platform located above the well, the conduit assemblycomprising at least an upper part of internal diameter allowing thetubular element to pass therethrough;

[0010] disconnecting the hanger from the tubular element; and

[0011] retrieving the tubular element through the conduit assembly tothe offshore platform.

[0012] By disconnecting the hanger from the tubular element andretrieving the tubular element through the conduit assembly withoutretrieving the hanger, it is achieved that a conduit assembly having atleast an upper part of relatively small diameter and consequently lowerweight can be applied.

[0013] Suitably said upper part of the conduit assembly includes anoffshore riser of smaller internal diameter than the outer diameter ofthe hanger.

[0014] In a preferred embodiment the conduit assembly further comprisesa lower part of internal diameter allowing the hanger to passtherethrough, whereby the passage in said lower part is in fluidcommunication with a space for storing the hanger so as to allow thetubular element to pass through the passage in said lower part when thehanger is stored in said space, the system further comprising movementmeans for moving the hanger into said space.

[0015] If, for example, the hanger has a central opening through whichthe tubular element can pass, the tubular element can be disconnectedfrom the hanger and retrieved through said opening of the hanger andthrough the conduit assembly to the offshore platform, while the hangerremains at the wellhead.

[0016] The invention will be described hereinafter in more detail and byway of example with reference to the accompanying drawings in which:

[0017]FIGS. 1-16 schematically show an embodiment of the system of theinvention during different stages of normal use thereof.

[0018] In the Figures, like reference numerals relate to likecomponents.

[0019] Referring to FIG. 1 there is shown a well 1 formed into an earthformation below a body of seawater 3. The well 1 is provided with awellhead 4 located at the earth surface 6, a hydrocarbon fluidproduction tubing 8 extending into the well 1, a tubing hanger 10 whichsuspends the tubing 8 at the wellhead 4, and a production tree 12(generally referred to as X-mas tree) arranged on top of the wellhead 4.Furthermore, the tubing 8 is provided with a subsurface safety valve(SSSV) 14 which is controlled by means of a hydraulic control line 16passing through the tubing hanger 10 to the production tree 12. Anoffshore platform 18 floats at the water surface 20.

[0020] Referring to FIG. 2, the offshore platform 18 is moved to aposition above the well 1, the production tree 12 is removed from thewellhead 4 by means of a running string 22.

[0021] Referring to FIG. 3, a conduit assembly 24 is lowered from theoffshore platform 18 above the wellhead 4. The conduit assembly 24 has alongitudinal through-passage (not shown) and includes an upper partformed of a riser 26, and a lower part formed of a housing 28 and ablowout preventor 30 (BOP). The internal diameter of the riser 26 islarger than the outer diameter of the tubing 8 so that the tubing 8 canpass through the riser 26. The internal diameter of the housing 28 andthe BOP 30 is larger than the outer diameter of the tubing hanger 10 sothat the tubing hanger 10 can pass through the BOP 30 and the housing28. The housing 28 is provided with a primary storage chamber 31 a forstoring the tubing hanger 10 and a secondary storage chamber 31 b inwhich a replacement tubing hanger (referred to hereinafter) is stored.Alternatively the housing 28 can be provided with several secondarystorage chambers, each being provided with a replacement tubing hanger.

[0022] Referring to FIG. 4, the BOP 30 is connected to the wellhead 4 sothat the passage of the conduit assembly 24 provides fluid communicationbetween the platform 18 and the wellhead 4.

[0023] Referring to FIG. 5, a retrieval/running string 32 (e.g. a drillpipe) provided with a latching mechanism for latching theretrieval/running string 32 to the tubing hanger 10 or to thereplacement tubing hanger, is lowered through the conduit assembly 24and latched to the tubing hanger 10. The retrieval/running string isfurther provided, at the lower end thereof, with a gripper device (notshown) for gripping the tubing 8, for example an internal “fishingspear”.

[0024] Referring to FIG. 6, the tubing hanger 10 together with thetubing 8 is pulled upwards until the tubing hanger 10 is in the housing28, and the tubing 8 is suspended from the BOP by closing the BOP rams34 against the tubing 8.

[0025] Referring to FIG. 7, a cutter (not shown) arranged in the housing28 is operated to cut the tubing 8 just below the tubing hanger 10 so asto cut the hanger 10 from the tubing 8. The retrieval/running string 32is raised a short distance. Instead of being arranged in the housing,the cutter can be lowered through the string 32 so as to cut the tubing8 from the inside.

[0026] Referring to FIG. 8, the tubing hanger 10 is moved into theprimary storage chamber 31 a by means of a movement device (not shown)provided in the housing 28, and the retrieval/running string 32 islowered to the upper end of the tubing 8 so as to grip the tubing 8 bymeans of the gripper device.

[0027] Referring to FIG. 9, the BOP rams 34 are opened and the tubing 8is pulled out of the well 1 and retrieved to the offshore platform 18 bymeans of the retrieval/running string 32.

[0028] Referring to FIG. 10, a new tubing 36 is lowered from theplatform 18 via the conduit assembly 24 into the well 1 by means of theretrieval/running string 32 (or another string). The new tubing isprovided with a new SSSV 38 and a corresponding new hydraulic controlline 40 capable of latching to the replacement tubing hanger (indicatedby reference sign 42). As indicated above, the replacement tubing hanger42 is stored in the secondary storage chamber 31 b. The upper end of thenew tubing 36 is provided with a latch connector (not shown) forlatching the replacement tubing hanger 42 to the new tubing 36.

[0029] Referring to FIG. 11, lowering of the new tubing 36 proceedsuntil its upper end is located in the housing 28, whereafter the BOPrams 34 are closed against the new tubing 36 so as to support the newtubing 36. The retrieval/running string 32 is disconnected from the newtubing 36 and raised a short distance, and the movement device moves thereplacement tubing hanger 42 from the secondary storage chamber 31 binto the through-passage of housing 28. The movement device then latchesthe replacement tubing hanger 42 to the new tubing 36 by means of thelatch connector, and the new hydraulic control line 40 latches to thereplacement tubing hanger 42.

[0030] Referring to FIG. 12, the string 32 is lowered so that thelatching mechanism of the string 32 latches to the replacement hanger42. The BOP rams 34 are opened, and the string 32 is further lowered sothat the replacement tubing hanger 42 together with the new tubing 36are lowered through the BOP 30 until the replacement tubing hanger 42becomes suspended at the wellhead 4.

[0031] Referring to FIG. 13, the string 32 is unlatched from thereplacement tubing hanger 42 and retrieved trough the conduit assembly24 to the offshore platform 18.

[0032] Referring to FIG. 14, the BOP 30 is disconnected from thewellhead 4, and the conduit assembly 24 is retrieved to the offshoreplatform.

[0033] Referring to FIGS. 15 and 16, the production tree 12 is loweredon running string 22 to the wellhead 4 and connected thereto, and thenew hydraulic control line 40 is connected to the production tree 12 inconventional manner.

[0034] It will be understood that the BOP rams 34 should be adapted tosuspend the new tubing 36 without crushing the new hydraulic controlline 40. This can, for example, be achieved by a suitable recessprovided in the BOP rams 34. Before closing the rams 34 against the newtubing 36, the latter would have to be oriented first so that the newhydraulic control line 40 is located opposite such recess.

1. A system for retrieving a tubular element extending into a subseawell provided with a wellhead, the tubular element being provided with ahanger suspending the tubular element at the wellhead, the hanger havinga larger outer diameter than the tubular element, the system comprising:a conduit assembly having a passage providing fluid communicationbetween the wellhead and an offshore platform located above the well,the conduit assembly comprising at least an upper part of internaldiameter allowing the tubular element to pass therethrough;disconnection means for disconnecting the hanger from the tubularelement; and retrieval means for retrieving the tubular element throughthe conduit assembly to the offshore platform, wherein said upper partof the conduit assembly includes an offshore riser of smaller internaldiameter than the outer diameter of the hanger, and wherein the conduitassembly further comprises a lower part which lower part is connected tothe wellhead.
 2. The system of claim 1, wherein the lower part is alower part of internal diameter allowing the hanger to passtherethrough, whereby the passage in said lower part is in fluidcommunication with a space for storing the hanger so as to allow thetubular element to pass through the passage in said lower part when thehanger is stored in said space, the system further comprising movementmeans for moving the hanger into said space.
 3. The system of claim 2,wherein said lower part of the conduit assembly includes a housingthrough which said passage extends, the housing being provided with astorage chamber defining said space.
 4. The system of claim 3, whereinsaid storage chamber is a primary storage chamber, and wherein thehousing is further provided with at least one secondary storage chamber,each secondary storage chamber being provided with a respectivereplacement hanger.
 5. The system of claims 3, wherein said lower partof the conduit assembly further includes a blowout preventor (BOP)through which said passage extends, the BOP being arranged below saidhousing.
 6. The system of claims 1, wherein the disconnecting means isselected from a cutter for cutting the hanger from the tubular elementand a device for unscrewing the hanger from the tubular element.
 7. Thesystem of claim 6, wherein the cutter is a jet cutter operable to cutthe tubular element by a stream of fluid jetted from the jet cutter. 8.The system of claim 6, wherein the disconnecting means comprises anelongate member extending through said upper conduit part, the elongatemember being provided with said one of a cutter and a device forunscrewing the hanger from the tubular element.
 9. The system of claims1, wherein the conduit assembly is provided with buoyancy means forproviding an upward force to the conduit assembly when submerged. 10.The system of claims 1, wherein the tubular element is a tubing for theproduction of hydrocarbon fluid from the well.
 11. A method ofretrieving a tubular element extending into a subsea well provided witha wellhead, the tubular element being provided with a hanger suspendingthe tubular element at the wellhead, the hanger having a larger outerdiameter than the tubular element, the method comprising: installing aconduit assembly having a passage so that the passage provides fluidcommunication between the wellhead and an offshore platform locatedabove the well, the conduit assembly comprising at least an upper partof internal diameter allowing the tubular element to pass therethroughand a lower part which is connected to the wellhead; disconnecting thehanger from the tubular element; and retrieving the tubular elementthrough the conduit assembly to the offshore platform wherein said upperpart of the conduit assembly includes an offshore riser of smallerinternal diameter than the outer diameter of the hanger.
 12. The methodof claim 11, wherein the lower part is a lower part of internal diameterallowing the hanger to pass therethrough, whereby the passage in saidlower part is in fluid communication with a space for storing the hangerso as to allow the tubular element to pass through the passage in saidlower part when the hanger is stored in said space, the system includingmovement means for moving the hanger into said space, and wherein themethod further comprises moving the hanger through said lower part ofthe conduit assembly and from there into space using the movement means.13. (Cancelled)
 14. (Cancelled)
 15. The system of claim 4, wherein saidlower part of the conduit assembly further includes a blowout preventor(BOP) through which said passage extends, the BOP being arranged belowsaid housing.
 16. The system of claim 2, wherein the disconnecting meansis selected from a cutter for cutting the hanger from the tubularelement and a device for unscrewing the hanger from the tubular element.17. The system of claim 3, wherein the disconnecting means is selectedfrom a cutter for cutting the hanger from the tubular element and adevice for unscrewing the hanger from the tubular element.
 18. Thesystem of claim 7, wherein the disconnecting means comprises an elongatemember extending through said upper conduit part, the elongate memberbeing provided with said one of a cutter and a device for unscrewing thehanger from the tubular element.
 19. The system of claim 2, wherein theconduit assembly is provided with buoyancy means for providing an upwardforce to the conduit assembly when submerged.